Relating Calories to Nutrients in the Food You Eat
Calories are simply a way to measure the energy in food and the energy released in the body. Although the technically correct name is kilocalorie, everyone, including dietitians, uses the shorter "calorie."
One calorie is the amount of energy necessary to raise the temperature of 1 gram of water by 1 degree Centigrade. You expend about 1 calorie per minute when sitting relaxed. That’s about the same amount of heat released by a candle or a 75-watt light bulb.
Calories are rounded on food labels, so when you multiply the grams of protein, carbohydrate, or fat, you may come out with a different value than appears on the label. Foods that contain 50 calories or fewer are rounded to the nearest 5-calorie increment; foods with more than 50 calories are rounded to the nearest 10-calorie increment.
Foods that have fewer than 5 calories can be listed as having 0 calories. Although you may think that this rounding seems misleading or inaccurate, keep in mind that a 10-calorie difference is actually negligible in the grand scheme of things.
A calorie isn’t a nutrient, but certain nutrients provide calories. Protein, carbohydrate, and fat make up the calorie contents of various foods. Although not considered a nutrient, alcohol also provides calories. In fact, one gram of
Protein contains 4 calories
Carbohydrate contains 4 calories
Fat contains 9 calories
Alcohol contains 7 calories
The remaining nutrients — water, minerals, and vitamins — do not provide calories, nor does fiber or cholesterol.
Few foods and beverages are 100 percent of any one nutrient. Most foods and beverages are a combination of protein, fat, and carbohydrate (and sometimes alcohol), so a food’s calorie count is the sum of the calories provided by each nutrient. See how it works:
A bowl of chicken noodle soup contains 3 grams of protein, 7 grams of carbohydrate, and 2 grams of fat for a total of 58 calories:
3 grams protein x 4 calories/gram = 12 calories
7 grams carbohydrate x 4 calories/gram = 28 calories
2 grams fat x 9 calories/gram = 18 calories
Total = 58 calories
Even though most foods are made up of two or more nutrients, foods are categorized by their predominant nutrient. For example, a bagel and a bowl of cereal are considered carbohydrate foods even though they also contain protein and, sometimes, fat. Even though a chicken breast is considered a protein food, not all of its calories come from protein. Chicken also contains fat, which contributes calories.
Not all calories are created equal. Foods that are considered empty-calorie foods really have nothing in them as far as nutrition goes, except for calories. Sugary foods, such as candy, are prime examples. When you’re restricting calories, you can make some room for empty-calorie foods but don’t build your diet on them. If you do, you’ll miss out on valuable minerals, fiber, and vitamins.
The opposite of empty-calorie foods are nutrient-dense foods. Calorie for calorie, they pack a solid nutrition punch by providing a good amount of vitamins, minerals, and/or fiber in comparison to the number of calories they provide. In other words, you get a big nutrition bang for your caloric buck.
An example of a nutrient-dense food is an orange. For a mere 60 calories, you get about 3 grams of fiber, 100 percent of your daily vitamin C requirement, and a good amount of folic acid plus a spectrum of other micronutrients and phytochemicals, such as antioxidants.